JP2004298920A - Method for manufacturing casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the filling property of casting sands into a mold by adding moisture and further alcohol to a refractory granular material for casting sands so as to improve the fluidity of the sands. <P>SOLUTION: In the manufacturing method for a casting mold, casting sands are manufactured by adding, in a binder coating process, a binder consisting essentially of a water-soluble inorganic sulfuric-acid compound, water, and alcohol to the refractory granular material for casting sands so as to coat the material with the binder. Thereby, the fluidity of the casting sands is improved and the filling property of the casting sands into a forming mold at a filling process is improved, so that the mold obtained by drying the casing sands in a drying process is almost prevented from producing casting defects. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１６】
ところで、これら無機硫酸化合物は、含有する結晶水の量により発現する強度にかなり差が出る。例えば、図２は、硫酸マグネシウムの水和量と鋳型強度の関係を示し、以下のような実験により得られたものである。即ち、耐火性粒状物としてフラタリー珪砂１００重量部を用い、これに硫酸マグネシウム・７水和物３重量部と水とを添加して鋳物砂とした。造型は直径３０ｍｍ、高さ５０ｍｍの試験片をＪＩＳ Ｚ ２６０１に定められる試験片搗き固め機を用いて３回搗き固めて成型し試験片とした。そして、出力７００Ｗのマイクロ波を照射して試験片を乾燥させた。
【００１７】
この際、乾燥時間（マイクロ波の照射時間）を調整することにより試験片中の硫酸マグネシウムが含有する結晶水量を変化させて、夫々の試験片の圧縮強度を測定した。試験片中の硫酸マグネシウムの結晶水量の算出は、マイクロ波乾燥後の試験片をさらに３００℃で硫酸マグネシウムが完全に無水和物となるまで乾燥させ、この乾燥前後で減った試験片の重量を、試験片内の硫酸マグネシウムが含有する結晶水の量とみなし、添加した硫酸マグネシウムの量からモル比により算出した。
【００１８】
硫酸マグネシウムの水和物は１，４，７及び１２水和物であるが、図２で示すように、約１〜６水和物のものが鋳型用として利用可能であり、さらに、強度が発現する好ましい範囲は１〜５水和物である。従って、乾燥状態で鋳型内の硫酸マグネシウムが１〜５水和物相当の結晶水を含有することが望ましい。さらに望ましくは、硫酸マグネシウムが２〜４水和物相当の結晶水を含有することが望ましい。
【００１９】
ところで、この水溶性の粘結剤を完全に溶解させるために、耐火性粒状物に相当量の水を添加する必要があるが、鋳物砂内部に含まれる水分により鋳物砂の流動性が悪くなり、次の充填工程において成形型に鋳物砂を充填するのが困難になる。そこで、この粘結剤被覆工程において、耐火性粒状物に対して水に加えてアルコールを添加することで、耐火性粒状物の表面張力を低下させて、成型型への鋳物砂の充填性を向上させる。
【００２０】
また、耐火性粒状物としては、図５のような珪砂の他、各粒子の表面に多数の気孔が形成されているために、これら気孔に水分を吸着させることが可能な、セラビーズ（図６（ａ），（ｂ）参照）等の吸水性を有する種々の耐火性粒状物を用いることもできる。このような吸水性の耐火性粒状物を用いて鋳物砂を作製した場合には、粘結剤を溶解させるために耐火性粒状物に加えられた水分の一部が、各粒子の気孔内に吸着されて粒子の表面に付着する水分が減少することになり、鋳物砂の流動性が改善され、次の充填工程における成形型への充填性が向上する。
【００２１】
次に、充填工程において、ブローイング造型により成形型内に鋳物砂を充填する。図３に示すように、水分除去工程で水分の少なくとも一部を除去された鋳物砂Ｓを成形型１の中子成形キャビティ２内に吹き込む。ここで、成形型１は、通気性を有するセラミック型であり、上下に２分割された型分割体１ａ，１ｂで構成され、成形型１は、マイクロ波を透過する合成樹脂製のケース部材３で覆われている。鋳物砂Ｓをキャビティ２内に充填する際には、成形型１の上側に設置したブローヘッド４内に加圧エアを作用させ、ブローノズル５を介して成形型１の内部に形成された中子成形キャビティ２内に鋳物砂Ｓを吹き込み、このキャビティ２内に鋳物砂Ｓを加圧充填して鋳物砂Ｓで所定の形状に造型する。
【００２２】
そして、乾燥工程において、鋳物砂にマイクロ波を照射して鋳物砂を乾燥させて鋳型を作る。図４に示すように、この乾燥工程においては、鋳物砂Ｓを充填した成形型１に対して均等にマイクロ波が照射されるようにスターラー６を回転させつつ、マグネトロン７からマイクロ波を所定時間照射する。このマイクロ波は成形型１を透過してキャビティ２内の鋳物砂Ｓに作用する。ここで、前記水分補給工程において水分を補給された鋳物砂Ｓ内には、自由水と無機硫酸化合物の結晶水という２つの状態で水分が存在するが、自由水の方が結晶水よりも誘電率が高いため、自由水が結晶水よりも先に蒸発しやすくなり、鋳物砂Ｓ内の無機硫酸化合物が少なくとも一部の結晶水を含有する状態を維持しつつ鋳物砂Ｓ内の自由水を蒸発させる。
【００２３】
鋳物砂内の水分が蒸発して発生した水蒸気は、吸引ポンプ８により吸引フード９、吸引ホース１０を介して成形型１の外部へ排出される。このようにして鋳物砂を乾燥させることで、乾燥状態において粘結剤の無機硫酸化合物が結晶水を含有することになって強度が発現するため、乾燥により得られる鋳型の強度を十分に確保することができる。
【００２４】
ここで、成形型１は通気性を有するセラミック型であり、蒸発した水分が成形型１から均等に外部へ放出されるため、無機硫酸化合物が含有する結晶水の量のばらつきを極力抑えて、得られた鋳型の強度を均一化することができる。
尚、キャビティ２を形成する成形型１は、セラミック型に限らず、合成樹脂製の型など、マイクロ波を透過するものであれば、他の材質のものでも使用できる。
【００２５】
次に、前述したように、粘結剤被覆工程において耐火性粒状物として吸水性の耐火性粒状物を使用した場合、あるいは、耐火性粒状物に水に加えてアルコールを添加して鋳物砂を作製した場合に、鋳物砂の充填性がどのように改善されるかを実験により検証した。
【００２６】
まず、耐火性粒状物として、図５に示すような表面に気孔のない珪砂（ウェドロン珪砂）と、図６〜図９に示すような、各粒子の表面が凸凹状に形成されており多数の気孔を有する吸水性の耐火性粒状物とを夫々使用し、これら耐火性粒状物に水だけを添加した場合について説明する。吸水性の耐火性粒状物としては、セラビーズ（図６）、セラミックビーズ（図７）、２種類のオーリチック砂１，２（図８、図９）を使用した。ここで、セラビーズやセラミックビーズは、カオリン、アルミナ等の微粒子を焼結して粒状としたものである。また、オーリチック砂は、生型で使用される生型砂より全粘土粉を除去したものであり、珪砂の回りに粘土が焼結してガラス状になったものが付着している。
【００２７】
そして、まず、これら耐火性粒状物の吸水性について実験した。図５の珪砂及び図６〜図９の吸水性の耐火性粒状物を夫々水中に１時間浸してから、ろ紙により表面の付着水を取り除き、その後、１１０℃で２時間乾燥させて、乾燥前後の重量の変化量から吸着水分量を求めた。その結果を表２に示す。
【００２８】
【表２】

【００２９】
表２において、珪砂中の水分は、珪砂の表面に付着している水分量であると考えられるが、その珪砂の水分量に対して、気孔を有する吸水性の耐火性粒状物の水分量は２倍以上であり、気孔を有する耐火性粒状物に水分が吸着されていることがわかる。
【００３０】
次に、吸水性の耐火性粒状物を用いた鋳物砂の圧縮強度と充填性について実験した。ここで、前述の吸水性実験で１時間水中に浸した後の珪砂及び吸水性の耐火性粒状物に、粘結剤としての硫酸マグネシウム・７水和物を１．４２５重量％及びリン酸二水素ナトリウムを０．０７５重量％と、所定量の水を加えて粘結剤を溶解させ、これらを混練して全体の水分量が０．５〜２．０重量％となるような鋳物砂を作製した。そして、この混練砂を３回ラミングしてφ３０ｍｍ×５０ｍｍの圧縮試験片を形成し、出力７００Ｗのマイクロ波により１分加熱して硬化させ、冷却後に強度測定を行った。
【００３１】
また、充填性の確認については、前記の鋳物砂を、ブロー成形機を用いてブロー圧２０ｐｓｉ（約０．１４Ｍｐａ）、ブロータイム０．５秒でブローイングして鋳型密度を求め、この値と、ＪＩＳＺ２６０１の試験片搗き固め器を用いて３回ラミングして成型した圧縮試験片の密度の比率から、以下のようにして充填率を算出した。
充填率（％）＝（ＪＩＳＺ２６０１によるラミング後の密度／ブロー成型後の密度）×１００
これら圧縮強度及び充填性に関する実験の結果を表３に示す。
【００３２】
【表３】

【００３３】
表３より、予め吸水させた吸水性を有する耐火性粒状物を用いた場合には、気孔を有さない珪砂を用いた場合に比べて鋳物砂の充填性が向上していることがわかる。しかし、セラミックビーズやオーリチック砂を用いた鋳物砂では、水分量が多く粘結剤が十分に溶解して各粒子に被覆されていると考えられる状態でも強度が不足しており、吸水性の耐火性粒状物の中では、セラビーズが最も実用に適していると思われる。従って、以下の実験では、吸水性を有する耐火性粒状物としてセラビーズを使用する。
【００３４】
以上の実験では、予め吸水させた耐火性粒状物に粘結剤と水とを加えて鋳物砂を作製したが、乾燥した珪砂及びセラビーズを、粘結剤（硫酸マグネシウム・７水和物１．４２５重量％、リン酸二水素ナトリウム０．０７５重量％）を溶解させた水溶液中に１時間浸してからろ紙により表面の付着水を取り除き、その後、１１０℃で２時間乾燥させて吸着水溶液量を測定し、さらに、その吸着水溶液中の吸着水分量を求めた。その結果を表４に示す。この場合でも、珪砂に対してセラビーズの吸着水分量は２倍以上であり、気孔を有するセラビーズに粘結剤の水溶液及び水分が吸着されていることがわかる。
【００３５】
【表４】

【００３６】
さらに、表４の吸水性実験と同様にして１時間水溶液中に浸した後の珪砂及びセラビーズを用いて、全体の水分量が０．５〜２．０重量％となるように鋳物砂を作製して、圧縮強度を測定するとともに充填率を算出すると、表５のようになる。
【００３７】
【表５】

【００３８】
表５より、気孔を有するセラビーズでは珪砂に比べて充填性が向上していることがわかる。また、粘結剤が十分に溶解するだけの水分量を与えると、圧縮強度はやや低めではあるが実用には耐えうる。
【００３９】
以上の実験により、耐火性粒状物にセラビーズを用いることにより、鋳物砂の充填性がある程度改善されることがわかる。しかし、気孔内の空隙が全体の体積の１０％弱もあるとされているセラビーズに対して、実際に吸着された水分量はかなり少ない（０．３８重量％）。これは、水の表面張力が高いために、気孔内に十分に水が浸透しないことが原因と考えられる。そこで、表面張力の低いアルコールを水と混ぜて混合溶液（水とアルコールの混合比率：７５対２５、または、５０対５０）を作り、この混合溶液中にセラビーズを浸して前述の実験と同様にして混合溶液の吸着量を測定し、測定された吸着量と混合溶液の混合比率とにより吸着水分量を求めた。その結果を表６に示す。
【００４０】
【表６】

【００４１】
表６より、水にセラビーズを浸透させた場合に比べて、水とエタノールの混合溶液、あるいは水とメタノールの混合溶液にセラビーズを浸透させた場合には、セラビーズへの吸着水分量が１．５倍程度増加しており、アルコールを添加することによりセラビーズに水分が吸着しやすくなることがわかる。
【００４２】
さらに、水とアルコールの混合溶液を吸着させたセラビーズを用いた鋳物砂の、圧縮強度及び充填性について実験を行った。ここで、圧縮強度の測定に関しては、水とアルコールの混合溶液を吸着させたセラビーズに、粘結剤（硫酸マグネシウム・７水和物１．４２５重量％、リン酸二水素ナトリウム０．０７５重量％）と所定量の水を加えて粘結剤を溶解させ、これらを混練して全体の水分量が０．５〜２．０重量％となるような鋳物砂を作製した。そして、この鋳物砂を密閉容器中で６０℃に昇温し、８０℃の金型中で３回ラミングして、φ２８ｍｍ×５０ｍｍの試験片を作製した。また、充填性に関しては、前述の水のみを吸着させた実験（表３）と同様にして鋳物砂の充填率を求めた。その結果を表７に示す。
【００４３】
【表７】

【００４４】
表７からわかるように、水とアルコールの混合溶液を吸着させたセラビーズを用いた場合には、水だけを吸着させた場合に比べて明らかに充填性が向上している。これは、水に比べて混合溶液の表面張力が低く、気孔内に水分が浸透しやすくなってセラビーズの各粒子の表面に付着する水分が減少することに加え、各粒子の表面においても表面張力が低下して各粒子の流動性が増すことに起因していると考えられる。
【００４５】
さて、以上の実験においては、耐火性粒状物として、セラビーズ等、各粒子が吸水性を有する耐火性粒状物を用いていたが、珪砂に粘結剤と水とアルコールとを加えて鋳物砂とした場合においても、強度及び充填性が改善されるかどうかを検証した。
【００４６】
まず、珪砂またはセラビーズに、硫酸マグネシウムとリン酸二水素ナトリウムからなる粘結剤と、水または水とエタノールの混合溶液を加えて鋳物砂とし、この鋳物砂を密閉容器中で６０℃に昇温し、８０℃の金型中で３回ラミングし、３０秒硬化させて、φ２８ｍｍ×５０ｍｍの試験片を作製した。尚、水だけを添加した場合には、ラミング後にエアパージを１５秒行って表面の水分を除去した。エタノールを添加した場合にはエアパージは行わなかった。これは、エタノールを添加した場合には水だけを添加した場合に比べて試験片の硬化が速かったためであるが、エタノールの比熱が水の比熱に比べて小さいことも影響していると思われる。その結果を表８に示す。
【００４７】
【表８】

【００４８】
珪砂に水とエタノールの混合溶液を加えて鋳物砂を作製した場合には、水のみを加えて鋳物砂を作製した場合に比べて充填性が向上している。さらに、エタノールの添加量が０．１重量％の場合では、添加した粘結剤の量にかかわらず鋳物砂の圧縮強度も向上している。
さらに、他の種類のアルコールとして、メタノール、イソプロピルアルコール（ＩＰＡ）を添加した場合、さらに、参考としてトルエンを添加した場合の、鋳物砂の圧縮強度と充填率を表９に示す。
【００４９】
【表９】

【００５０】
メタノール、ＩＰＡを添加した場合においても、水のみを加えた場合に比べて充填性が向上し、アルコールの添加量が０．１重量％の場合においては圧縮強度も１割以上上昇している。但し、トルエンを添加した場合には充填性についての効果は認められない。
尚、エタノールやメタノール、ＩＰＡ等のアルコールの添加量が多い場合には、鋳物砂を乾燥して鋳型を硬化させる際に、アルコールが急激に気化して鋳型が崩れやすくなる虞があるため、乾燥工程においては、鋳物砂の加熱を緩やかに行って鋳物砂の温度を急激に上げないようにすることが望ましい。
【００５１】
ところで、表８、表９において、耐火性粒状物に、０．１重量％程度のアルコールを水とともに加えると、水のみを加えた場合に比べて圧縮強度が大きくなっている。これは、次のような要因によるものと考えられる。
【００５２】
前述したように、硫酸マグネシウム等の無機硫酸化合物を主体とする粘結剤を用いた鋳物砂は、無機硫酸化合物が結晶水を有する水和物の状態で強度が発現する。ところで、例えば、硫酸マグネシウムは、温度により、無水和物から１２水和物までの種々の状態で存在し、−３．８〜１．８℃では１２水和物、１．８〜４８．３℃では７水和物、４８．３〜６８℃では６水和物、２００℃以上で無水和物となる。そして、最も強度が発現する２〜４水和物となるのは、８０℃前後の温度にある場合と考えられる。
【００５３】
ところで、メタノール、エタノール、ＩＰＡの沸点は、夫々６５．６℃、７８．３℃、８２．７℃であるため、図１０に示すように、水とアルコールを混合させた混合溶液を加熱していくと、８０℃前後の温度で気液平衡の状態となり、この８０℃前後の温度状態がしばらく続くことになる。従って、乾燥工程において、耐火性粒状物に粘結剤と水とアルコールを加えて作製した鋳物砂を乾燥する際に、鋳物砂の温度が８０℃前後となる可能性が高くなり、乾燥後の鋳型内の硫酸マグネシウムが２〜４水和物の状態で存在しやすくなる。
【００５４】
以上説明した鋳造用鋳型の製造方法によれば、次のような効果が得られる。
１）粘結剤被覆工程において、水に加えてアルコールを耐火性粒状物に加えることで、耐火性粒状物の各粒子の表面の表面張力が低下するため、成形型への鋳物砂の充填性を向上させることができる。また、アルコールを適量加えることにより鋳型の強度を向上させることも可能になる。
【００５５】
２）粘結剤被覆工程において、耐火性粒状物として各粒子が吸水性を有する耐火性粒状物を用いることで、粘結剤を溶解させるために加えられた水分の一部が、耐火性粒状物の各粒子に吸収され、各粒子の表面に存在する水分の量が減少するため、各粒子の表面張力が低下して鋳物砂の充填性が向上する。
【００５６】
次に、前記実施形態に種々の変更を加えた変更形態について説明する。
１］粘結剤被覆工程において耐火性粒状物に加えるアルコールとしては、前述のメタノール、エタノール、ＩＰＡの他、プロピルアルコール、ブチルアルコール、アミルアルコール、アリルアルコール等、他の低級アルコールを用いてもよい。さらに、高級アルコールを用いても同様の効果が得られる可能性がある。
【００５７】
２］前記実施形態では、耐火性粒状物として珪砂単独、あるいは、吸水性を有するセラビーズを単独で使用しているが、複数種類の耐火性粒状物を混合して使用してもよい。
３］乾燥工程における、鋳物砂の乾燥方法としては、前述のマイクロ波や過熱蒸気による乾燥の他、鋳型に温風を供給してその熱により水分を蒸発させる方法、金型を加熱してその中に鋳物砂を充填して硬化させる方法、成形型内に鋳物砂を充填させた後に減圧して水分を蒸発させる方法などを適用できる。さらに、これらの方法を組み合わせて適用してもよい。
【００５８】
４］鋳物砂あるいは粘結剤には、鋳造欠陥を防止するために通常鋳物砂に添加されるベンガラ、鉄粉、石炭粉、黒鉛粉、木粉、タルク、澱粉、穀物粉、シリカフラワー、ジルコンフラワー、オリビンフラワーなどを所定量配合できる。
【００５９】
さらに、鋳物砂あるいは粘結剤には、型への充填性を改善するために、無機潤滑剤として二硫化タングステン、二硫化モリブデン、有機潤滑剤として炭化水素系、ポリアルキレングリコール、シリコーン系、フッ素系、フェニルエーテル、リン酸エステル潤滑剤を所定量配合できる。
さらに、鋳型にはアルコール性塗型、水性塗型、粉末塗型、表面安定剤、ひけ防止用テルル粉末などの通常、鋳型表面に塗布する造型材料を用いることができる。
【００６０】
【発明の効果】請求項１の発明によれば、粘結剤被覆工程において、水に加えてアルコールを鋳物砂用耐火性粒状物に加えるので、鋳物砂用耐火性粒状物の各粒子の表面の表面張力が低下するため、成形型への鋳物砂の充填性を向上させることができる。
【００６１】
請求項２の発明によれば、粘結剤被覆工程において鋳物砂用耐火性粒状物に加えられた水分の一部が、鋳物砂用耐火性粒状物の各粒子に吸収されて、各粒子の表面に存在する水分の量が減少するため、各粒子の表面張力が低下して鋳物砂の充填性が向上する。
【００６２】
請求項３の発明によれば、無機硫酸化合物に硫酸マグネシウムが含まれ、この硫酸マグネシウムは水に対する溶解性が良好であるため、硫酸マグネシウムを含む粘結剤を用いることで水溶性の鋳造用鋳型を製造することができ、注湯後に水を加えるだけで鋳型を崩壊させて粘結剤を回収することも容易になる。
【００６３】
請求項４の発明によれば、乾燥工程において鋳物砂にマイクロ波を照射して鋳物砂を乾燥させるので、鋳物砂内の無機硫酸化合物が少なくとも一部の結晶水を含有する状態を維持しつつ水を除去することが可能になり、鋳型の乾燥状態において無機硫酸化合物を水和物の状態で存在させて、鋳型の強度を発現させることができる。
【００６４】
請求項５の発明によれば、乾燥工程で鋳物砂を乾燥する際に、蒸発した水分を通気性のセラミック型から均等に外部へ放出させることができるため、鋳型の強度を均一化することができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る水溶性鋳造用鋳型の製造方法を示す工程図である。
【図２】硫酸マグネシウム水和物と圧縮強度の関係を示す図である。
【図３】充填工程における鋳物砂の型への充填作業を説明する説明図である。
【図４】乾燥工程におけるマイクロ波による乾燥作業を説明する説明図である。
【図５】電子顕微鏡による珪砂の粒子全体の写真である。
【図６】セラビーズの粒子の写真であり、（ａ）は粒子全体の写真、（ｂ）は粒子表面を拡大した写真である。
【図７】セラミックビーズの粒子の写真であり、（ａ）は粒子全体の写真、（ｂ）は粒子表面を拡大した写真である。
【図８】オーリチック砂（オーリチック砂１）の粒子の写真であり、（ａ）は粒子全体の写真、（ｂ）は粒子表面を拡大した写真である。
【図９】別のオーリチック砂（オーリチック砂２）の粒子の写真であり、（ａ）は粒子全体の写真、（ｂ）は粒子表面を拡大した写真である。
【図１０】水とアルコールの混合溶液の温度変化を示す図である。
【符号の説明】
Ｓ 鋳物砂
１ 成形型
２ キャビティ[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a casting mold, and more particularly to a method using a water-soluble binder.
[0002]
2. Description of the Related Art Conventionally, as a method of manufacturing a casting mold, a water-soluble binder and water are added to refractory granules for molding sand to form molding sand, and the molding sand is filled into a molding die. There is a method of obtaining a mold by molding. For example, a method for producing a water-soluble casting mold using a binder mainly composed of an inorganic sulfate compound such as magnesium sulfate which is easily soluble in water as a water-soluble binder has been proposed (eg, And Patent Document 1).
[0003]
[Patent Document 1] JP-A-53-119724 (page 1-2)
[0004]
In the method of manufacturing a mold described in Patent Document 1, a binder is used to surely coat a water-soluble binder on the surface of the refractory granules for molding sand. It is necessary to add an amount of water capable of dissolving the binder together with the binder. In other words, the molding sand is in a so-called wet sand state containing water, so that the molding sand has a low fluidity, and when the molding sand is filled into the molding die as it is, particularly, a molding die having a complicated shape. When it is filled, the filling property is deteriorated. When the casting metal is filled with a casting metal, the casting metal is liable to be poorly filled. At the time of casting, casting defects such as seizure defects, sand biting defects, cracking defects, and deformation may occur. is there.
[0005]
An object of the present invention is to improve the flowability of molding sand and improve the filling property of molding sand into a mold.
[0006]
According to a first aspect of the present invention, there is provided a method for manufacturing a casting mold, wherein the casting sand is molded to produce a casting mold. A binder coating step of adding a binder mainly composed of a soluble inorganic sulfate compound, water and alcohol, and coating the binder on the refractory granules for molding sand to form molding sand, and a molding die for molding molding sand. And a drying step of drying the foundry sand filled in the molding die.
[0007]
In the method for producing a casting mold, in a binder coating step, a refractory granule for molding sand is added by adding a binder mainly composed of a water-soluble inorganic sulfate compound and water to the refractory granule for molding sand. The molding is coated with a binder dissolved in water to produce molding sand. Here, as the binder, various kinds of sulfate compounds exhibiting water solubility such as magnesium sulfate, aluminum sulfate, sodium sulfate, potassium sulfate, nickel sulfate and the like can be used alone or in combination. Then, after the molding sand is filled in the molding die in the filling step, the molding sand filled in the molding die in the drying step is dried to complete the production of the mold.
[0008]
By the way, in the binder coating step, the filling property of the foundry sand is deteriorated because water is added to the foundry sand in order to dissolve the binder, but the amount of water added to improve the filling property is reduced. If the amount is reduced, the binder mainly composed of an inorganic sulfate compound may not be sufficiently coated on the surface of each particle of the refractory granules for molding sand, and the mold may not have sufficient strength. Therefore, in the binder coating step, alcohol is added to the refractory granules for foundry sand in addition to water to lower the surface tension of the surface of each particle of the refractory granules for foundry sand, and to a molding die. Improves the fillability of foundry sand.
[0009]
According to a second aspect of the present invention, there is provided a method for manufacturing a casting mold according to the first aspect, wherein each particle of the refractory granular material for foundry sand has water absorbency. Therefore, a part of the moisture added to the refractory granules for foundry sand in the binder coating step is absorbed by each particle of the refractory granules for foundry sand, and the amount of moisture present on the surface of each particle Is reduced, the surface tension of each particle is reduced, and the filling property of molding sand into the mold is improved.
[0010]
According to a third aspect of the present invention, in the method for manufacturing a casting mold according to the first or second aspect, the inorganic sulfate compound includes magnesium sulfate. Since magnesium sulfate has good solubility in water, it is possible to produce a water-soluble casting mold by using a binder containing this magnesium sulfate. It is also easy to collect the binder and use the binder repeatedly.
[0011]
According to a fourth aspect of the present invention, there is provided a method of manufacturing a casting mold according to any one of the first to third aspects, wherein in the drying step, the molding sand is irradiated with microwaves to dry the molding sand. In general, when the foundry sand is dried in the drying step, the strength of the mold is higher when the inorganic sulfate compound is present in the form of a hydrate having water of crystallization than in the anhydrous form. . Therefore, when the molding sand is irradiated with microwaves in the drying step, the moisture in the molding sand has a higher dielectric constant than the water of crystallization of the inorganic sulfate compound, and thus tends to evaporate earlier than the water of crystallization. Water can be removed while maintaining at least a part of water of crystallization, and the inorganic sulfate compound can be present in a hydrated state when the mold is in a dry state.
[0012]
According to a fifth aspect of the present invention, there is provided a method of manufacturing a casting mold according to the first to fourth aspects, wherein the mold is a ceramic mold having air permeability. Therefore, when the foundry sand is dried in the drying step, the evaporated water can be uniformly discharged from the air-permeable ceramic mold to the outside, so that the strength of the mold can be made uniform.
[0013]
Embodiments of the present invention will be described below. The present invention is an example applied to a method for producing a water-soluble casting mold for producing an aluminum alloy casting mold by molding molding sand.
As shown in FIG. 1, this method for producing a water-soluble casting mold is characterized in that a refractory granule for molding sand (hereinafter referred to as a refractory granule) is made of a binder mainly composed of a water-soluble inorganic sulfate compound and water. And the alcohol are added, and the refractory granules are coated with a binder to form a molding sand, a binder coating step, a molding step of filling the molding sand with the molding sand, and drying the molding sand filled in the molding die. Drying step.
[0014]
First, in a binder coating step, refractory granules such as silica sand, a binder mainly composed of a water-soluble inorganic sulfate compound, and an amount of water capable of dissolving the binder are added and mixed. Then, the surface of the refractory granules is coated with a binder dissolved in water to form molding sand. Here, it is desirable that the inorganic sulfate compound contained in the binder has a melting point of 770 ° C. or more, which is an average pouring temperature of aluminum alloy casting, and is easily soluble in water. Specifically, magnesium sulfate, aluminum sulfate, sodium sulfate, nickel sulfate, manganese sulfate and the like shown in Table 1 are used. By using a binder mainly composed of such an easily soluble inorganic sulfate compound, it is possible to collect the binder by simply adding water after pouring, collect the binder, and repeatedly use the binder. It will be easier.
[0015]
[Table 1]

[0016]
By the way, these inorganic sulfate compounds vary considerably in the strength to be developed depending on the amount of crystallization water contained. For example, FIG. 2 shows the relationship between the amount of hydration of magnesium sulfate and the mold strength, which was obtained by the following experiment. That is, 100 parts by weight of flattery silica sand was used as the refractory granules, and 3 parts by weight of magnesium sulfate heptahydrate and water were added thereto to obtain molding sand. For molding, a test piece having a diameter of 30 mm and a height of 50 mm was crushed and molded three times using a test piece crusher specified in JIS Z 2601 to obtain a test piece. Then, the test piece was dried by irradiating a microwave having an output of 700 W.
[0017]
At this time, the compressive strength of each test piece was measured by changing the amount of water of crystallization contained in magnesium sulfate in the test piece by adjusting the drying time (microwave irradiation time). The amount of water of crystallization of magnesium sulfate in the test piece was calculated by further drying the test piece after microwave drying at 300 ° C. until magnesium sulfate was completely anhydrate, and then reducing the weight of the test piece before and after drying. The amount of crystallization water contained in the magnesium sulfate in the test piece was considered, and the molar ratio was calculated from the amount of magnesium sulfate added.
[0018]
The hydrates of magnesium sulfate are 1,4,7 and 12 hydrates. As shown in FIG. 2, those of about 1 to 6 hydrates can be used as a mold, The preferred range of expression is 1 to pentahydrate. Therefore, it is desirable that the magnesium sulfate in the mold in a dry state contains water of crystallization equivalent to 1 to 5 hydrate. More preferably, it is desirable that the magnesium sulfate contains water of crystallization equivalent to 2 to 4 hydrate.
[0019]
By the way, in order to completely dissolve this water-soluble binder, it is necessary to add a considerable amount of water to the refractory granules, but the fluidity of the molding sand deteriorates due to the moisture contained in the molding sand. In addition, it becomes difficult to fill the molding die with the molding sand in the next filling step. Therefore, in this binder coating step, by adding alcohol to the refractory granules in addition to water, the surface tension of the refractory granules is reduced, and the filling property of the molding sand into the molding die is improved. Improve.
[0020]
As the refractory granular material, in addition to silica sand as shown in FIG. 5, since a large number of pores are formed on the surface of each particle, Cerabeads (FIG. 6) capable of adsorbing moisture to these pores. (Refer to (a) and (b).) Various refractory granules having water absorbency can also be used. When casting sand is produced using such water-absorbing refractory granules, part of the water added to the refractory granules to dissolve the binder is contained in the pores of each particle. The amount of water adsorbed and adhering to the surface of the particles is reduced, the flowability of the molding sand is improved, and the filling property of the molding die in the next filling step is improved.
[0021]
Next, in a filling step, molding sand is filled in the mold by blowing molding. As shown in FIG. 3, the casting sand S from which at least a part of the moisture has been removed in the moisture removing step is blown into the core molding cavity 2 of the mold 1. Here, the molding die 1 is a ceramic mold having air permeability, and is composed of vertically divided mold divided bodies 1a and 1b. The molding die 1 is made of a synthetic resin case member 3 that transmits microwaves. Covered with. When the molding sand S is filled into the cavity 2, pressurized air is applied to the blow head 4 installed above the molding die 1, and the air formed inside the molding die 1 via the blow nozzle 5 is blown. The molding sand S is blown into the child molding cavity 2, the molding sand S is filled into the cavity 2 under pressure, and the molding sand S is molded into a predetermined shape.
[0022]
Then, in a drying step, the molding sand is dried by irradiating the molding sand with microwaves to form a mold. As shown in FIG. 4, in this drying step, while rotating the stirrer 6 so that the mold 1 filled with the molding sand S is evenly irradiated with the microwave, the microwave is emitted from the magnetron 7 for a predetermined time. Irradiate. This microwave transmits through the mold 1 and acts on the molding sand S in the cavity 2. Here, in the foundry sand S to which water has been replenished in the water replenishment step, water exists in two states: free water and crystallization water of the inorganic sulfate compound. Since the rate is high, the free water is more likely to evaporate before the crystallization water, and the free water in the molding sand S is removed while maintaining the state in which the inorganic sulfate compound in the molding sand S contains at least a part of the crystallization water. Allow to evaporate.
[0023]
The water vapor generated by evaporating the water in the casting sand is discharged to the outside of the mold 1 by the suction pump 8 via the suction hood 9 and the suction hose 10. By drying the foundry sand in this way, the inorganic sulfate compound of the binder contains water of crystallization in the dry state and the strength is developed, so that the strength of the mold obtained by drying is sufficiently ensured. be able to.
[0024]
Here, the mold 1 is a ceramic mold having air permeability, and since the evaporated water is uniformly released from the mold 1, the dispersion of the amount of crystal water contained in the inorganic sulfate compound is minimized. The strength of the obtained mold can be made uniform.
The mold 1 for forming the cavity 2 is not limited to a ceramic mold, but may be made of another material such as a synthetic resin mold as long as it transmits microwaves.
[0025]
Next, as described above, in the case of using a water-absorbing refractory granule as the refractory granule in the binder coating step, or adding alcohol in addition to water to the refractory granule to remove molding sand. It was verified by experiments how the filling property of the foundry sand was improved in the case of the production.
[0026]
First, as refractory granules, silica sand (wedron silica sand) having no pores on the surface as shown in FIG. 5 and a large number of particles each having a rough surface as shown in FIGS. The case where water-absorbing refractory granules having pores are used, respectively, and only water is added to these refractory granules will be described. Cerabeads (FIG. 6), ceramic beads (FIG. 7), and two types of auritic sands 1 and 2 (FIGS. 8 and 9) were used as the water-absorbing refractory granules. Here, the ceramic beads or ceramic beads are obtained by sintering fine particles of kaolin, alumina, or the like to form granules. Further, the auritic sand is obtained by removing all clay powders from the green sand used in the green mold, and the clay formed by sintering the clay around the silica sand adheres.
[0027]
First, an experiment was conducted on the water absorption of these refractory granules. The silica sand of FIG. 5 and the water-absorbing refractory granules of FIGS. 6 to 9 are respectively immersed in water for 1 hour, and then water adhering to the surface is removed with a filter paper, and then dried at 110 ° C. for 2 hours. The amount of adsorbed water was determined from the change in the weight of the sample. Table 2 shows the results.
[0028]
[Table 2]

[0029]
In Table 2, the water content in the quartz sand is considered to be the moisture content adhering to the surface of the quartz sand, and the moisture content of the water-absorbing refractory granular material having pores is smaller than the moisture content of the quartz sand. It is more than twice, and it can be seen that moisture is adsorbed on the refractory granules having pores.
[0030]
Next, an experiment was conducted on the compressive strength and fillability of the molding sand using the water-absorbing refractory granules. Here, 1.425% by weight of magnesium sulfate heptahydrate as a binder and 1.425% by weight of diphosphate were added to the silica sand and the water-absorbing refractory granules immersed in water for 1 hour in the above-mentioned water absorption experiment. 0.075% by weight of sodium hydrogen and a predetermined amount of water are added to dissolve the binder, and these are kneaded to form a molding sand having a total water content of 0.5 to 2.0% by weight. Produced. Then, the kneaded sand was rammed three times to form a compression test piece of φ30 mm × 50 mm, heated and cured by a microwave having an output of 700 W for 1 minute, and after cooling, strength was measured.
[0031]
In order to confirm the filling property, the molding sand was blown using a blow molding machine at a blow pressure of 20 psi (approximately 0.14 Mpa) and a blow time of 0.5 second to obtain a mold density. The filling rate was calculated as follows from the ratio of the density of the compressed test piece molded by ramming three times using a test piece crusher of JISZ2601.
Filling rate (%) = (density after ramming according to JISZ2601 / density after blow molding) × 100
Table 3 shows the results of experiments on these compressive strengths and filling properties.
[0032]
[Table 3]

[0033]
From Table 3, it can be seen that the use of the refractory granules having water absorbency which has been absorbed in advance has improved the filling property of the molding sand as compared with the case where silica sand having no pores is used. However, molding sand using ceramic beads or auritic sand has insufficient strength even when it is considered that the amount of water is large and the binder is sufficiently dissolved to cover each particle, and the water absorption Among the granular materials, Cera beads seems to be most suitable for practical use. Therefore, in the following experiments, Celabeads are used as refractory granules having water absorption.
[0034]
In the above experiment, a molding sand was prepared by adding a binder and water to the refractory granules previously absorbed in water, but dried silica sand and celabeads were mixed with the binder (magnesium sulfate heptahydrate 1. (425% by weight, 0.075% by weight of sodium dihydrogen phosphate) for 1 hour, remove water adhering to the surface with a filter paper, and then dry at 110 ° C for 2 hours to reduce the amount of the adsorbed aqueous solution. The amount of water adsorbed in the aqueous solution was determined. Table 4 shows the results. Even in this case, the amount of adsorbed water of the cerabeads is more than twice as large as the silica sand, and it can be seen that the aqueous solution of the binder and the water are adsorbed to the cerabeads having pores.
[0035]
[Table 4]

[0036]
Furthermore, molding sand was prepared using silica sand and celabeads immersed in an aqueous solution for one hour in the same manner as in the water absorption experiment in Table 4 so that the total water content was 0.5 to 2.0% by weight. Then, when the compressive strength is measured and the filling rate is calculated, the results are as shown in Table 5.
[0037]
[Table 5]

[0038]
From Table 5, it can be seen that the packing property of the cerabeads having pores is improved as compared with silica sand. Also, when a sufficient amount of water is given to the binder to dissolve it sufficiently, the compressive strength is slightly lower, but it can withstand practical use.
[0039]
From the above experiments, it can be seen that the use of celabeads for the refractory granules improves the filling property of the foundry sand to some extent. However, the amount of water actually adsorbed is considerably small (0.38% by weight) with respect to cerabeads in which pores in pores are less than 10% of the total volume. This is considered to be because water does not sufficiently penetrate into pores due to high surface tension of water. Therefore, an alcohol having a low surface tension is mixed with water to form a mixed solution (mixing ratio of water and alcohol: 75:25, or 50:50), and serabeads are immersed in the mixed solution and the same as in the above experiment. The amount of adsorbed water of the mixed solution was measured by the above method, and the amount of adsorbed water was obtained from the measured amount of adsorbed liquid and the mixing ratio of the mixed solution. Table 6 shows the results.
[0040]
[Table 6]

[0041]
As shown in Table 6, the amount of water adsorbed on the cerabeads was 1.5 times higher when the cerabeads were permeated into a mixed solution of water and ethanol or a mixed solution of water and methanol than when the cerabeads were permeated into water. This indicates that the addition of alcohol makes it easier for water to be adsorbed on the CERABEADS.
[0042]
Further, experiments were conducted on the compressive strength and filling property of molding sand using cerabeads to which a mixed solution of water and alcohol was adsorbed. Here, regarding the measurement of the compressive strength, the binder (1.425% by weight of magnesium sulfate heptahydrate, 0.075% by weight of sodium dihydrogen phosphate) was added to the sera beads adsorbing the mixed solution of water and alcohol. ) And a predetermined amount of water were added to dissolve the binder, and these were kneaded to prepare a molding sand having a total water content of 0.5 to 2.0% by weight. Then, the molding sand was heated to 60 ° C. in a closed container and rammed three times in a mold at 80 ° C. to produce a test piece of φ28 mm × 50 mm. Regarding the filling property, the filling rate of the molding sand was determined in the same manner as in the above-described experiment in which only water was adsorbed (Table 3). Table 7 shows the results.
[0043]
[Table 7]

[0044]
As can be seen from Table 7, the use of cerabeads adsorbed with a mixed solution of water and alcohol clearly improves the filling property as compared to the case where only water is adsorbed. This is because the surface tension of the mixed solution is lower than that of water, and water easily penetrates into the pores, reducing the amount of water adhering to the surface of each particle of CERABEADS. This is considered to be due to the fact that the fluidity of each particle increases due to the decrease of
[0045]
By the way, in the above experiments, as the refractory granules, refractory granules such as celabeads, each particle of which has a water absorbing property, are used.However, a molding sand is obtained by adding a binder, water and alcohol to silica sand. Also in this case, it was verified whether the strength and the filling property were improved.
[0046]
First, a binder made of magnesium sulfate and sodium dihydrogen phosphate and a mixed solution of water or water and ethanol are added to silica sand or cerabeads to form molding sand, and the molding sand is heated to 60 ° C. in a closed vessel. Then, it was rammed three times in a mold at 80 ° C. and cured for 30 seconds to produce a test piece of φ28 mm × 50 mm. When only water was added, air purging was performed for 15 seconds after ramming to remove water on the surface. No air purge was performed when ethanol was added. This is because the test piece hardened faster when ethanol was added than when only water was added, but it seems that the specific heat of ethanol is also smaller than that of water. . Table 8 shows the results.
[0047]
[Table 8]

[0048]
In the case of producing a molding sand by adding a mixed solution of water and ethanol to silica sand, the filling property is improved as compared with the case of producing a molding sand by adding only water. Further, when the amount of ethanol added is 0.1% by weight, the compressive strength of the foundry sand is improved regardless of the amount of the binder added.
Further, Table 9 shows the compressive strength and the filling rate of the molding sand when methanol and isopropyl alcohol (IPA) were added as other types of alcohol, and when toluene was further added as a reference.
[0049]
[Table 9]

[0050]
Even when methanol and IPA were added, the filling property was improved as compared with the case where only water was added, and the compressive strength was increased by 10% or more when the amount of alcohol added was 0.1% by weight. However, when toluene is added, no effect on the filling property is recognized.
In addition, when a large amount of alcohol such as ethanol, methanol, or IPA is added, when the molding sand is dried to harden the mold, the alcohol may be rapidly vaporized and the mold may be easily broken. In the process, it is desirable to slowly heat the molding sand so that the temperature of the molding sand does not rise rapidly.
[0051]
By the way, in Tables 8 and 9, when about 0.1% by weight of alcohol is added to the refractory granules together with water, the compressive strength is higher than when only water is added. This is considered to be due to the following factors.
[0052]
As described above, molding sand using a binder mainly composed of an inorganic sulfate compound such as magnesium sulfate develops strength in a hydrate state in which the inorganic sulfate compound has water of crystallization. By the way, for example, magnesium sulfate exists in various states from anhydrate to dodecahydrate depending on the temperature, and at -3.8 to 1.8 ° C, dodecahydrate and 1.8 to 48.3. At 7C, it becomes a heptahydrate, at 48.3-68C, it becomes a hexahydrate, and at 200C or more, it becomes an anhydrate. It is considered that the 2- to 4-hydrate exhibiting the highest strength is at a temperature of about 80 ° C.
[0053]
Incidentally, since the boiling points of methanol, ethanol, and IPA are 65.6 ° C., 78.3 ° C., and 82.7 ° C., respectively, as shown in FIG. As the temperature rises, a gas-liquid equilibrium state is established at a temperature of about 80 ° C., and this temperature state of about 80 ° C. continues for a while. Therefore, in the drying step, when drying the foundry sand prepared by adding a binder, water and alcohol to the refractory granules, the temperature of the foundry sand is likely to be around 80 ° C. Magnesium sulfate in the mold is likely to be present in the form of 2-4 hydrate.
[0054]
According to the method for manufacturing a casting mold described above, the following effects can be obtained.
1) In the binder coating step, by adding alcohol to the refractory granules in addition to water, the surface tension of the surface of each particle of the refractory granules is reduced, so that the filling of the molding sand with the molding sand is reduced. Can be improved. Further, by adding an appropriate amount of alcohol, the strength of the mold can be improved.
[0055]
2) In the binder coating step, by using the refractory granules in which each particle has a water absorbing property as the refractory granules, a part of the water added to dissolve the binder is converted into the refractory granules. Since the amount of water absorbed by each particle of the product and present on the surface of each particle is reduced, the surface tension of each particle is reduced and the filling property of molding sand is improved.
[0056]
Next, modified embodiments in which various modifications are made to the above-described embodiment will be described.
1] As the alcohol added to the refractory granules in the binder coating step, other lower alcohols such as propyl alcohol, butyl alcohol, amyl alcohol and allyl alcohol may be used in addition to the above-mentioned methanol, ethanol, and IPA. . Furthermore, a similar effect may be obtained by using a higher alcohol.
[0057]
2] In the above embodiment, silica sand alone or water-absorbing cerabeads is used alone as the refractory granules, but a plurality of types of refractory granules may be used in combination.
3] As a method of drying the foundry sand in the drying step, in addition to the drying by the above-described microwave or superheated steam, a method of supplying hot air to the mold to evaporate moisture by the heat, heating the mold and heating the mold. A method in which the molding sand is filled therein and cured, a method in which the molding sand is filled in the molding die, and the pressure is reduced to evaporate the moisture can be applied. Furthermore, you may apply combining these methods.
[0058]
4] Foundry sands or binders include bengara, iron powder, coal powder, graphite powder, wood powder, talc, starch, cereal powder, silica flour, zircon which are usually added to molding sand to prevent casting defects. A predetermined amount of flower, olivine flower and the like can be blended.
[0059]
In addition, in order to improve the filling property of the molding sand or binder, tungsten disulfide and molybdenum disulfide are used as inorganic lubricants, and hydrocarbon-based, polyalkylene glycol, silicone-based, and fluorine-based are used as organic lubricants. System, phenyl ether, phosphate ester lubricant can be blended in a predetermined amount.
Further, a molding material usually applied to the surface of the mold such as an alcoholic mold, an aqueous mold, a powder mold, a surface stabilizer, and tellurium powder for preventing sink marks can be used for the mold.
[0060]
According to the first aspect of the present invention, in the binder coating step, alcohol is added to the refractory granules for foundry sand in addition to water, so that the surface of each particle of the refractory granules for foundry sand is improved. Since the surface tension of the molding sand decreases, the filling property of the molding sand with the molding sand can be improved.
[0061]
According to the invention of claim 2, a part of the water added to the refractory granules for foundry sand in the binder coating step is absorbed by each particle of the refractory granules for foundry sand, Since the amount of water present on the surface is reduced, the surface tension of each particle is reduced, and the filling property of the molding sand is improved.
[0062]
According to the invention of claim 3, magnesium sulfate is contained in the inorganic sulfate compound, and since this magnesium sulfate has good solubility in water, a water-soluble casting mold can be obtained by using a binder containing magnesium sulfate. Can be produced, and it becomes easy to recover the binder by disintegrating the mold simply by adding water after pouring.
[0063]
According to the invention of claim 4, since the molding sand is irradiated with microwaves in the drying step to dry the molding sand, the inorganic sulfate compound in the molding sand maintains at least a part of water of crystallization. Water can be removed, and the strength of the template can be developed by allowing the inorganic sulfate compound to be present in a hydrated state when the template is in a dry state.
[0064]
According to the invention of claim 5, when the foundry sand is dried in the drying step, the evaporated moisture can be uniformly discharged from the permeable ceramic mold to the outside, so that the strength of the mold can be made uniform. it can.
[Brief description of the drawings]
FIG. 1 is a process chart showing a method for producing a water-soluble casting mold according to an embodiment of the present invention.
FIG. 2 is a graph showing the relationship between magnesium sulfate hydrate and compressive strength.
FIG. 3 is an explanatory diagram for explaining a filling operation of a molding sand into a mold in a filling step.
FIG. 4 is an explanatory diagram illustrating a drying operation using microwaves in a drying step.
FIG. 5 is a photograph of the whole silica sand particles taken by an electron microscope.
FIGS. 6A and 6B are photographs of the particles of cerabeads, wherein FIG. 6A is a photograph of the entire particle and FIG. 6B is a photograph in which the particle surface is enlarged.
FIGS. 7A and 7B are photographs of the particles of the ceramic beads, in which FIG. 7A is a photograph of the entire particle and FIG. 7B is a photograph in which the particle surface is enlarged.
FIG. 8 is a photograph of particles of auritic sand (Auritic sand 1), (a) is a photograph of the whole particle, and (b) is a photograph in which the particle surface is enlarged.
FIG. 9 is a photograph of particles of another auritic sand (Auritic sand 2), (a) is a photograph of the whole particle, and (b) is a photograph in which the particle surface is enlarged.
FIG. 10 is a diagram showing a temperature change of a mixed solution of water and alcohol.
[Explanation of symbols]
S Foundry sand 1 Mold 2 Cavity

Claims (5)

In a method of manufacturing a casting mold to produce a casting mold by molding casting sand,
Binder for molding sand by adding a binder mainly composed of water-soluble inorganic sulfate compound, water and alcohol to the refractory granules for foundry sand and coating the binder on the refractory granules for foundry sand A coating process;
A filling step of filling molding sand with molding sand,
A drying step of drying the foundry sand filled in the mold,
A method for producing a casting mold, comprising: The method for producing a casting mold according to claim 1, wherein each particle of the refractory granular material for foundry sand has water absorbency. The method for producing a casting mold according to claim 1, wherein the inorganic sulfate compound includes magnesium sulfate. The method for producing a casting mold according to any one of claims 1 to 3, wherein in the drying step, the molding sand is irradiated with microwaves to dry the molding sand. The method for producing a casting mold according to any one of claims 1 to 4, wherein the mold is a ceramic mold having air permeability.

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